Secondary Steelmaking: Principles and Applications

308 Pages·2000·17.38 MB·English

by  Ahindra Ghosh

SECONDARY
STEELMAKING
Principles and Applications
Ahindra Ghosh, Sc.D.
AICTE Emeritus Fellow
Professor (Retired)
Indian Institute of Technology, Kanpur
Department of Materials and Metallurgical Engineering
CRC Press
Boca Raton London New York Washington, D.C.
©2001 CRC Press LLC
0264 Disclaimer Page 1 Thursday, November 2, 2000 11:07 AM
Library of Congress Cataloging-in-Publication Data
Ghosh, Ahindra
Secondary Steelmaking : Principles and Applications
p. cm.
Includes bibliographical references and index.
ISBN 0-8493-0264-1
1. Steel. I. Title.
TN730 .G48 2000
672—dc21 00-060865
This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with
permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish
reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials
or for the consequences of their use.
Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior
permission in writing from the publisher.
The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works,
or for resale. Specific permission must be obtained in writing from CRC Press LLC for such copying.
Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431.
Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for
identification and explanation, without intent to infringe.
© 2001 by CRC Press LLC
No claim to original U.S. Government works
International Standard Book Number 0-8493-0264-1
Library of Congress Card Number 00-060865
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
Printed on acid-free paper
©2001 CRC Press LLC
Dedication
to
Dr. G. P. Ghosh
(Late) Prof. T. B. King
(Late) Prof. A. K. Seal
©2001 CRC Press LLC
Preface
With the passage of time, customers who buy steel are becoming more and more quality conscious.
In view of this, steelmakers are attempting to improve steel quality as a continuing endeavor. The
product of steelmaking is liquid steel, which is then cast primarily via the continuous casting route.
Liquid steel of superior quality should have a minimum of harmful impurities and nonmetallic
inclusions, the desired alloying element content and casting temperature, and good homogeneity.
The primary steelmaking furnaces, such as the basic oxygen furnace and electric arc furnace,
are not capable of meeting quality demands. This has led to the growth of what is known as
secondary steelmaking, which is concerned with further refining and processing of liquid steel after
it is tapped into the ladle from the primary steelmaking furnace. Secondary steelmaking is a major
thrust area in modern steelmaking technology and has witnessed significant advances in the last
30 years. Its scope is wide and includes deoxidation, degassing, desulfurization, homogenization,
temperature control, removal, and modifications of inclusions, etc.
This text consists of 11 chapters. The first chapter provides a brief overview of secondary
steelmaking. Chapters 2 through 4 briefly review relevant scientific fundamentals, viz., thermody-
namics, fluid flow, mixing, mass transfer, and kinetics relevant to secondary steelmaking. Chapters
5 through 10 deal with reactions, phenomena, and processes that are of concern in secondary
steelmaking.
Since some topics do not justify a full chapter for each, a chapter on miscellaneous topics
(Chapter 8) provides coverage of these issues. The technology to manufacture what is known as
clean steel calls for a variety of measures at different processing stages. An attempt has been made
to present an integrated picture of this in Chapter 10.
Mathematical modeling is an important component of process research nowadays. The basics
as relevant to secondary steelmaking, along with application examples, are presented in Chapter 11.
Although the present text deals primarily with principles and applications for the secondary
steelmaking processes, it contains brief information on the processes and modern technological
advances as well. Synthesis of science with technology is one of the objectives. The textbook style
of writing has been adopted. Some examples and their solutions also have been included. References
have been included at the end of each chapter. Hence, the author hopes that this text will be found
useful not only by students and teachers, but also by steelmakers and research and development
engineers interested in the field.
Ahindra Ghosh
©2001 CRC Press LLC
Acknowledgments
The author gratefully acknowledges the contribution of his colleague Dr. D. Mazumdar, who wrote
Chapter 11 and provided help in other aspects, and assistance provided by Dr. S. K. Choudhary,
Dr. T. K. Roy, Mr. K. Deo, Mr. A. Sharma, and Ms. S. Ghosh at certain stages of preparation of
the manuscript. Thanks are due to Mr. B. D. Biswas and Mr. J. L. Kuril for careful typing of the
manuscript, Mr. A. K. Ganguly for tracing figures, and Dr. M.N. Mungole for helping with
photographs. Financial assistance from the Centre for Development of Technical Education, Indian
Institute of Technology, Kanpur, is gratefully acknowledged. Lastly, the work would not have been
possible without the patience and cooperation of author’s wife Radha and other members of his
family.
©2001 CRC Press LLC
About the Author
Professor Ahindra Ghosh was born at Howrah, West Bengal, India, in
1937. He studied for his B.E. degree in Metallurgical Engineering at
Bengal Engineering College and received the degree from Calcutta
University in 1958. Subsequently, he received his Sc.D. degree from
the Massachusetts Institute of Technology in 1963, specializing in
extractive metallurgy. He served as Research Associate at Ohio State
University, U.S.A., from 1963–64. Since 1964, he has been with the
Department of Materials and Metallurgical Engineering, Indian Insti-
tute of Technology, Kanpur, where he retired as Professor in June,
2000, and is currently an Emeritus Fellow of All India Council of
Technical Education. During this period, he also has spent short periods
at the Imperial College, London, as well as the Massachusetts Institute
of Technology as a visiting scientist; and at Metallurgical and Engineering Consultants, Ranchi,
and Tata Research Development and Design Centre, Pune, as an advisor.
Professor Ghosh has guided many research students and scholars. He has to his credit 2 books
and about 75 original research publications in reviewed journals. He also has delivered invited
lectures at many conferences and has published several review papers in conference proceedings,
etc. For the last three decades, his principal interest has been in the theory of metallurgical processes
in ironmaking and steelmaking, with specific emphasis on sponge ironmaking, secondary steel-
making, ingot casting, and continuous casting. In these endeavors, Professor Ghosh also had
significant interaction with industry in addition to his work with metallurgical fundamentals. He
is also involved in basic research in solidification of metals and high-temperature oxidation of alloys.
Professor Ghosh has served as an editor of the Transactions of the Indian Institute of Metals
and as a member or advisor for many professional activities. In recognition, he has been elected a
Fellow of the Indian National Academy of Engineering for his distinguished contribution to
engineering.
©2001 CRC Press LLC
Contents
Preface
About the Author
List of Symbols with Units
Chapter 1 Introduction
1.1 History of Secondary Steelmaking
1.2 Trends in Steel Quality Demands
1.3 Scientific Fundamentals
1.4 Process Control
References
Chapter 2 Thermodynamic Fundamentals
2.1 Introduction
2.2 First and Second Laws of Thermodynamics
2.3 Chemical Equilibrium
2.4 ∆G0 for Oxide Systems
2.5 Activity–Composition Relationships: Concentrated Solutions
2.6 Activity–Composition Relationships: Dilute Solutions
2.7 Chemical Potential and Equilibrium
2.8 Slag Basicity and Capacities
References
Appendix 2.1
Appendix 2.2
Appendix 2.3
Appendix 2.4
Chapter 3 Flow Fundamentals
3.1 Basics of Fluid Flow
3.2 Fluid Flow in Steel Melts in Gas-Stirred Ladles
References
Appendix 3.1
Chapter 4 Mixing, Mass Transfer, and Kinetics
4.1 Introduction
4.2 Mixing in Steel Melts in Gas-Stirred Ladles
4.3 Kinetics of Reactions among Phases
©2001 CRC Press LLC
4.4 Mass Transfer in a Gas-Stirred Ladle
4.5 Mixing vs. Mass Transfer Control
References
Appendix 4.1
Chapter 5 Deoxidation of Liquid Steel
5.1 Thermodynamics of Deoxidation of Molten Steel
5.2 Kinetics of the Deoxidation of Molten Steel
5.3 Deoxidation in Industry
References
Appendix 5.1
Chapter 6 Degassing and Decarburization of Liquid Steel
6.1 Introduction
6.2 Thermodynamics of Reactions in Vacuum Degassing
6.3 Fluid Flow and Mixing in Vacuum Degassing
6.4 Rates of Vacuum Degassing and Decarburization
6.5 Decarburization for Ultra-Low Carbon (ULC) and Stainless Steel
References
Chapter 7 Desulfurization in Secondary Steelmaking
7.1 Introduction
7.2 Thermodynamic Aspects
7.3 Desulfurization with Only Top Slag
7.4 Injection Metallurgy for Desulfurization
References
Chapter 8 Miscellaneous Topics
8.1 Introduction
8.2 Gas Absorption during Tapping and Teeming from Surrounding Atmosphere
8.3 Temperature Changes of Molten Steel during Secondary Steelmaking
8.4 Phosphorus Control in Secondary Steelmaking
8.5 Nitrogen Control in Steelmaking
8.6 Application of Magnetohydrodynamics
References
Chapter 9 Inclusions and Inclusion Modification
9.1 Introduction
9.2 Influence of Inclusions on the Mechanical Properties of Steel
9.3 Inclusion Identification and Cleanliness Assessment
9.4 Origin of Nonmetallic Inclusions
9.5 Formation of Inclusions during Solidification
9.6 Inclusion Modification
References
Chapter 10 Clean Steel Technology
10.1 Introduction
©2001 CRC Press LLC
10.2 Summary of Earlier Chapters
10.3 Refractories for Secondary Steelmaking
10.4 Tundish Metallurgy for Clean Steel
References
Chapter 11 Modeling of Secondary Steelmaking Processes
Dipak Mazumdar, Ph.D.
11.1 Introduction
11.2 Modeling Techniques
11.3 Modeling Turbulent Fluid Flow Phenomena
11.4 Modeling of Material and Thermal Mixing Phenomena
11.5 Modeling of Heat and Mass Transfer between Solid Additions and Liquid Steel
11.6 Numerical Considerations
11.7 Concluding Remarks
References
©2001 CRC Press LLC
List of Symbols with Units*
a specific surface area m–1
a acceleration vector ms–2
A area m2
a activity of component i in a solution —
i
Bi Biot number —
C specific heat Jmol–1K–1, Jkg–1K–1
C drag coefficient —
D
C concentration of component i in solution kg m–3
i
slag capacity for component i —
d diameter m
D molecular diffusivity of species i m2 s–1
i
D turbulent diffusivity m2 s–1
t
E internal energy, activation energy Jmol–1
energy input in a gas-stirred bath J
ej first-order interaction coefficient describing influence of solute j on f —
i i
Eu Euler number —
F view factor —
F, F force, force vector N
F drag force N
D
f activity coefficient of solute i in a solution in 1 wt.pct. standard state —
i
Fr Froude number —
Fr modified Froude number —
m
g acceleration due to gravity ms–2
G Gibbs free energy Jmol–1, J
GO Gibbs free energy at standard state Jmol–1, J
∆G, ∆GO finite change in G, GO Jmol–1, J
G partial molar Gibbs free energy of component i in solution Jmol–1
i
Gm partial molar Gibbs free energy of mixing of component i in solution J mol–1
i
Gr Grasshof number —
H enthalpy J mol–1, J
height of liquid bath m
h activity of solute i in a solution in 1 wt.% standard state —
i
* — indicates a dimensionless quantity, mol means gram · mole.
©2001 CRC Press LLC